The present invention relates to an arrangement for flow regulation and for opening a flow-through conduit for liquids under pressure, in particular carbonated water, including a discharge shutoff valve that can be controlled by an actuation device and of a flow regulating valve that provides a constant flow independently of the pressure of the incoming liquid.
Such an arrangement is used to keep a constant rate of flow of liquids per unit of time to achieve, in combination with a time limit on the delivery of the liquid, high precision in the volume of liquid to be dispensed. For example, in beverage dispensers, in which soft drinks are mixed and prepared from carbonated water and beverage concentrates, it is required that the preset mixing ratio of both components be followed as closely as possible, since otherwise a change in taste would result and strongly influence the quality of the soft drink.
For beverage concentrates to be mixed in relatively small amounts, usually a volumetric feed is used and thus also a high precision in the volume dispensed is achieved.
To achieve also the required precision of the volume dispensed with respect to the carbonated water and thus the desired mixing ratio, it is required that both parameters that determine the volume, namely the flow rate and the inflow time, be established as precisely as possible. The flow-through time can be controlled relatively well by open-close valves, although the closing and opening operations represent disturbances for relatively short release times.
Controlling the flow rate is considerably more problematic. Briefly occurring pressure variations an temperature variations must also be taken into consideration. Likewise, with gaseous liquids, the liquid-gas mixture tends to degas because of pressure drop, flow turbulences, and warming in the area of a flow regulating valve.
In beverage dispensers, the carbonated water is mixed in a carbonator from water and CO.sub.2 gas, is stored under pressure and cooled to near the freezing point. When carbonated water is dispensed, considerable pressure variations occur. The release is performed in the range of atmospheric, i.e., constant, pressure. With prolonged nonoperating times, the flow regulating valve is warmed to room temperature, and by the release of carbonated water it is cooled to below 0.degree. C. Therefore, demanding requirements are placed on such a regulating valve. But as an object to be produced economically, it should also be inexpensive.
From German patent P 34 30 953 there is already known an arrangement for mixing liquids with a pressure-independent flow regulating valve. The flow-regulating valve includes a movable piston located in a cylindrical piston chamber and upon which the restoring force of a spring acts. The flow medium flows through a central bore in the piston to discharge openings in the cylinder, which are partly covered by the piston regulating edge. The spring raises the counterforce to the pressure of the medium and establishes the working pressure. Between piston and cylinder a gap is provided that has a sealing function. Thus the gap is small and has a narrow tolerance. Contaminations between piston and cylinder disturb the function of the regulation and lead to incorrect releases or to failure of the arrangement. In addition, the relatively complex design of the known regulating valve, because of numerous individual components that also move, involves the danger of a failure of the overall arrangement if even one individual component is impaired in its ability to function.